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Speed in Gears

posted 25 Dec 2011, 04:25 by NOC NSW   [ updated 25 Dec 2011, 04:48 ]

The following is based on information taken from the Cycleserv publication: Norton Commando ‘S’ Type, Roadster, Fastback (Page 66).  It is based on standard gear ratios and sprockets with 19” wheels and a 4.10 section rear tyre.  The only variable is the number of teeth on the gearbox sprocket.  My Commando is now fitted with a 20 tooth gearbox sprocket, down from the 22 tooth sprocket with which it came.

 1.   Number of Gearbox Sprocket Teeth = 19 and Top Gear Ratio = 4.84:1 = 15.429 mph/1,000 revs in Top Gear (or 24.857 km/h).  It = 108 mph @ 7,000 rpm.

 

Fourth Gear

Third Gear

Second Gear

Revs

Mph

Mph

Mph

 

 

 

 

1,500

 23.14

19.07

13.50

2,000

 30.86

25.42

18.00

2,500

 38.57

31.78

22.50

3,000

 46.29

38.13

27.00

3,500

 54.00

44.49

31.50

4,000

 61.72

50.84

36.00

4,500

 69.43

57.19

40.50

5,000

 77.15

63.55

45.00

5,500

 84.86

69.91

49.50

6,000

 92.57

76.26

54.00

6,500

100.29

82.62

58.50

7,000

108.00

88.97

63.00

2.   Number of Gearbox Sprocket Teeth = 20 and Top Gear Ratio = 4.60:1 = 16.286 mph/1,000 revs in Top Gear (or 26.286 km/h).  It = 114 mph @ 7,000 rpm.

 

Fourth Gear

Third Gear

Second Gear

Revs

Mph

Mph

Mph

 

 

 

 

1,500

 24.43

20.14

14.35

2,000

 35.57

26.86

19.14

2,500

 40.72

33.58

23.93

3,000

 48.86

40.29

28.72

3,500

 57.00

47.00

33.50

4,000

 65.14

53.72

38.28

4,500

 73.29

60.44

43.07

5,000

 81.43

67.15

47.86

5,500

 89.57

73.87

52.64

6,000

 97.72

80.58

57.43

6,500

105.86

87.29

62.21

7,000

114.00

94.00

67.00

 3.   Number of Gearbox Sprocket Teeth = 21 and Top Gear Ratio = 4.38:1 = 17.000 mph/1,000 revs in Top Gear (or 27.286 km/h).  It = 119 mph @ 7,000 rpm. 

 

Fourth Gear

Third Gear

Second Gear

Revs

Mph

Mph

Mph

 

 

 

 

1,500

 25.50

21.21

15.00

2,000

 34.00

28.28

20.00

2,500

 42.50

35.35

25.00

3,000

 51.00

42.42

30.00

3,500

 59.50

49.49

35.00

4,000

 68.00

56.56

40.00

4,500

 76.50

63.63

45.00

5,000

 85.00

70.70

50.00

5,500

 93.50

77.77

55.00

6,000

102.00

84.84

60.00

6,500

110.50

91.91

65.00

7,000

119.00

99.00

70.00

Perce Butterworth